Many varied applications utilize sensing means for detecting the position of a rotary or linear actuator to either merely detect such displacement or utilize a signal generated to perform a control function. For many years the preferred sensing means has been electrical wherein the displacement being sensed is converted to an electrical signal. Such apparatus are accurate and have found widespread acceptance.
However, in certain applications it is undesirable and/or unreliable to employ electronic components due to surrounding conditions in which the sensing transducing means are exposed. Therefore it would be highly desirable to provide means to hydraulically sense displacement and transduce the displacement to a proportional pressure signal for position indication or control purposes.
While the fluid power art is very old, prior to the present invention there has been a long unfilled need for an accurate, reliable and relatively simple apparatus for hydraulically sensing and transducing displacement of an actuator to provide a proportional pressure signal, particularly for pilot control functions utilizing low fluid flows.